This application claims the benefit of Japanese Patent Application No. 2006-019854, filed Jan. 27, 2006, which is incorporated herein by reference.
1. Field of the Invention
Embodiments of the invention relate to an ink-jet head and an ink-jet recording device provided with that head.
2. Description of the Related Art
Various ink-jet ejection systems may be used in the ink-jet head of an ink-jet recording device. In one type of ink-jet ejection system, a piezo system, a piezoelectric element is widely utilized to exert pressure on the ink and cause its ejection from a nozzle. A representative ink-jet head of the piezo system is configured such that an ink in an ink chamber provided therein moves into a pressure chamber via a connection passage, and further moves into a nozzle in communication with the pressure chamber, and is finally ejected on a recording medium from an aperture of a tip of the nozzle. An ejection pressure is applied to the ink in the pressure chamber by deformation of a piezoelectric actuator which covers the pressure chamber. Deformation of this piezoelectric actuator is caused by applying a voltage to it.
An ink-jet recording device provided with such an ink-jet head may be use to achieve printing with a higher resolution. In order to achieve this, the ink should be ejected as a smaller droplet, for example a droplet of several pl (picoliters), from the nozzle. For that reason, it is desirable to make an aperture diameter of the tip of the nozzle (such as, the nozzle diameter) smaller than the related-art diameter of from about 30 to 50 μm (from 10 to 50 pl in the resulting droplet).
However, when the nozzle diameter is made small, an ink present in an ejection hole in the nozzle tip or an ink droplet attached in the surroundings of the ejection hole is likely to dry out. This often results in ejection failure. In order to improve such ejection failure, it may be possible to lower a viscosity of the ink by, for example, increasing the amount of a solvent. However, when the viscosity of the ink is lowered, because the vibration of a meniscus hardly ceases, stable ink ejection is difficult.